scholarly journals Modelling ground motion in the Hutt Valley, New Zealand

2007 ◽  
Vol 40 (4) ◽  
pp. 190-199
Author(s):  
Shu Qin Ma ◽  
Martha Savage ◽  
Jiashun Yu
Keyword(s):  
New Zealand ◽  
Ground Motion ◽  
Synthetic Seismograms ◽  
Spectral Ratios ◽  
Amplification Factors ◽  
Earthquake Scenarios ◽  
Seismic Arrays ◽  
Ground Motion Amplification ◽  
The North ◽  
The City

The Hutt Valley is an alluvial basin that hosts the city of Lower Hutt, in the North Island, New Zealand. The basin is bounded by the Wellington Fault on its northwest side, and exhibits ground motion amplification factors up to about 15, measured by several seismic experiments using weak motion and portable seismic arrays during 1990-1991. Synthetic seismograms computed by using local 1D stratigraphic models under each station reproduce qualitatively the amplitudes and durations of the corresponding observed seismograms at most of the soft site stations of the arrays. Amplification factors estimated from spectral ratios of the synthetic seismograms are up to about 9. The authors present comparisons of amplification between synthetics and observations, allowing a “calibration” of the model so that it could be used to determine more realistic ground amplifications for earthquake scenarios.

Distribution of ground-motion intensity inferred from questionnaire survey, earthquake recordings, and microtremor measurements—A case study in Christchurch, New Zealand, during the 1994 arthurs pass earthquake

1997 ◽  
Vol 87 (2) ◽  
pp. 356-369
Author(s):  
Takumi Toshinawa ◽  
J. John Taber ◽  
John B. Berrill
Keyword(s):  
New Zealand ◽  
Ground Motion ◽  
Intensity Data ◽  
Amplification Factors ◽  
Areal Distribution ◽  
Local Site ◽  
Geological Conditions ◽  
The City ◽  
Microtremor Measurements

Abstract The areal distribution of seismic ground-motion intensity in the city of Christchurch, New Zealand, during the 1994 Arthurs Pass Earthquake (ML 6.6) was evaluated using an intensity questionnaire together with local site amplifications inferred from seismic recordings and microtremors. In order to estimate the intensity in parts of the city where no intensity data were available, intensity data were compared to relative levels of shaking determined from both weak-motion and microtremor recordings. Weak ground-motion amplification factors were determined using ratios of ground accelerations at five sediment sites with respect to a rock site. Microtremor amplification factors were determined from horizontal-to-vertical spectral ratios at a 1-km spacing throughout the city. A positive correlation between weak-motion and microtremor amplification factors allowed extrapolation of microtremor amplification to estimated MM intensity (EMMI). EMMI ranged from 3 to 6 and was consistent with the questionnaire intensity and geological conditions and showed detailed information on the areal distribution of ground-motion intensity in the city.

scholarly journals Spatial Distribution of Lichens in Metrosideros excelsa in Northern New Zealand Urban Forests

Diversity ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 170
Author(s):  
Gladys N. Benitez ◽  
Glenn D. Aguilar ◽  
Dan Blanchon
Keyword(s):  
Spatial Distribution ◽  
Species Richness ◽  
New Zealand ◽  
Lichen Species ◽  
Positive Correlation ◽  
Breast Height ◽  
Lichen Community ◽  
The North ◽  
The City ◽  
Lichen Flora

The spatial distribution of corticolous lichens on the iconic New Zealand pōhutukawa (Metrosideros excelsa) tree was investigated from a survey of urban parks and forests across the city of Auckland in the North Island of New Zealand. Lichens were identified from ten randomly selected trees at 20 sampling sites, with 10 sites classified as coastal and another 10 as inland sites. Lichen data were correlated with distance from sea, distance from major roads, distance from native forests, mean tree DBH (diameter at breast height) and the seven-year average of measured NO2 over the area. A total of 33 lichen species were found with coastal sites harboring significantly higher average lichen species per tree as well as higher site species richness. We found mild hotspots in two sites for average lichen species per tree and another two separate sites for species richness, with all hotspots at the coast. A positive correlation between lichen species richness and DBH was found. Sites in coastal locations were more similar to each other in terms of lichen community composition than they were to adjacent inland sites and some species were only found at coastal sites. The average number of lichen species per tree was negatively correlated with distance from the coast, suggesting that the characteristic lichen flora found on pōhutukawa may be reliant on coastal microclimates. There were no correlations with distance from major roads, and a slight positive correlation between NO2 levels and average lichen species per tree.

scholarly journals Historical Earthquake Scenarios for the Middle Strand of the North Anatolian Fault Deduced from Archeo-Damage Inventory and Building Deformation Modeling

2020 ◽  
Vol 92 (1) ◽  
pp. 583-598
Author(s):  
Yacine Benjelloun ◽  
Julia de Sigoyer ◽  
Hélène Dessales ◽  
Laurent Baillet ◽  
Philippe Guéguen ◽  
...  
Keyword(s):  
Historical Earthquakes ◽  
Historical Seismicity ◽  
North Anatolian Fault ◽  
First Century ◽  
Building Vulnerability ◽  
Earthquake Scenarios ◽  
The North ◽  
Seismicity Catalog ◽  
Quality Ranking ◽  
The City

Abstract The city of İznik (ancient Nicaea), located on the middle strand of the North Anatolian fault zone (MNAF), presents outstanding archeological monuments preserved from the Roman and Ottoman periods (first to fifteenth centuries A.D.), bearing deformations that can be linked to past seismic shaking. To constrain the date and intensity of these historical earthquakes, a systematic survey of earthquake archeological effects (EAEs) is carried out on the city’s damaged buildings. Each of the 235 EAEs found is given a quality ranking, and the corresponding damage is classified according to the European Macroseismic Scale 1998 (EMS-98). We show that the walls oriented north–south were preferentially damaged, and that most deformations are perpendicular to the walls’ axes. The date of postseismic repairs is constrained with available archeological data and new C14 dating of mortar charcoals. Three damage episodes are evidenced: (1) between the sixth and late eighth centuries, (2) between the nineth and late eleventh centuries A.D., and (3) after the late fourteenth century A.D. The repartition of damage as a function of building vulnerability points toward a global intensity VIII on the EMS-98. The 3D modeling of a deformed Roman obelisk shows that only earthquakes rupturing the MNAF can account for this deformation. Their magnitude can be bracketed between Mw 6 and 7. Our archeoseismological study complements the historical seismicity catalog and confirms paleoseismological data, suggesting several destructive earthquakes along the MNAF, since the first century A.D. We suggest the fault might still have accumulated enough stress to generate an Mw 7+ rupture.

Evaluation of amplitude-scaled and spectrum-matched motions to estimate ground-motion amplification factors

2020 ◽  
Vol 18 (10) ◽  
pp. 4659-4679
Author(s):  
Bo Li ◽  
Yang Lu ◽  
Mahesh D. Pandey ◽  
Gao Ma ◽  
Yang Liu ◽  
...  
Keyword(s):  
Ground Motion ◽  
Amplification Factors ◽  
Ground Motion Amplification

Ensemble ShakeMaps for Magnitude 9 Earthquakes on the Cascadia Subduction Zone

2020 ◽  
Vol 92 (1) ◽  
pp. 199-211
Author(s):  
Erin A. Wirth ◽  
Alex Grant ◽  
Nasser A. Marafi ◽  
Arthur D. Frankel
Keyword(s):  
Ground Motion ◽  
Strong Motion ◽  
Sedimentary Basins ◽  
Earthquake Rupture ◽  
Logic Tree ◽  
Ground Shaking ◽  
Amplification Factors ◽  
Earthquake Scenarios ◽  
The Pacific ◽  
Tree Approach

Abstract We develop ensemble ShakeMaps for various magnitude 9 (M 9) earthquakes on the Cascadia megathrust. Ground-shaking estimates are based on 30 M 9 Cascadia earthquake scenarios, which were selected using a logic-tree approach that varied the hypocenter location, down-dip rupture limit, slip distribution, and location of strong-motion-generating subevents. In a previous work, Frankel et al. (2018) used a hybrid approach (i.e., 3D deterministic simulations for frequencies <1  Hz and stochastic synthetics for frequencies >1  Hz) and uniform site amplification factors to create broadband seismograms from this set of 30 earthquake scenarios. Here, we expand on this work by computing site-specific amplification factors for the Pacific Northwest and applying these factors to the ground-motion estimates derived from Frankel et al. (2018). In addition, we use empirical ground-motion models (GMMs) to expand the ground-shaking estimates beyond the original model extent of Frankel et al. (2018) to cover all of Washington State, Oregon, northern California, and southern British Columbia to facilitate the use of these ensemble ShakeMaps in region-wide risk assessments and scenario planning exercises. Using this updated set of 30 M 9 Cascadia earthquake scenarios, we present ensemble ShakeMaps for the median, 2nd, 16th, 84th, and 98th percentile ground-motion intensity measures. Whereas traditional scenario ShakeMaps are based on a single hypothetical earthquake rupture, our ensemble ShakeMaps take advantage of a logic-tree approach to estimating ground motions from multiple earthquake rupture scenarios. In addition, 3D earthquake simulations capture important features such as strong ground-motion amplification in the Pacific Northwest’s sedimentary basins, which are not well represented in the empirical GMMs that compose traditional scenario ShakeMaps. Overall, our results highlight the importance of strong-motion-generating subevents for coastal sites, as well as the amplification of long-period ground shaking in deep sedimentary basins, compared with previous scenario ShakeMaps for Cascadia.

3D Physics-Based Numerical Simulations of Ground Motion in Istanbul from Earthquakes along the Marmara Segment of the North Anatolian Fault

2020 ◽  
Vol 110 (5) ◽  
pp. 2559-2576 ◽  
Author(s):  
Maria Infantino ◽  
Ilario Mazzieri ◽  
Ali Güney Özcebe ◽  
Roberto Paolucci ◽  
Marco Stupazzini
Keyword(s):  
Numerical Simulations ◽  
Ground Motion ◽  
Prediction Models ◽  
Seismic Source ◽  
North Anatolian Fault ◽  
Empirical Prediction ◽  
Earthquake Scenarios ◽  
The North ◽  
Specific Geometry ◽  
Directivity Effects

ABSTRACT In this article, the outcomes of a research cooperation between Politecnico di Milano, Italy, and Munich RE, Germany, aiming to improve ground-motion estimation in the Istanbul area through 3D physics-based numerical simulations (PBSs), are illustrated. To this end, 66 PBSs were run, considering earthquake scenarios of magnitude ranging from Mw 7 to 7.4 along the North Anatolian fault (NAF; Turkey), offshore Istanbul. The present article focuses on the detailed introduction of the simulated scenarios comprising: (1) the setup of the 3D numerical model, (2) the validation of the model with recordings of a recent earthquake, (3) the PBSs results, (4) a parametric study on the effect of different features of the seismic source, and (5) a comparison with well-established ground-motion prediction equations to highlight the main differences resulting from the use of a standard empirical approach as opposed to physics-based “source-to-site” numerical simulations. As a main outcome of this study, we observed as, for magnitude Mw 7 and 7.2, PBSs are in agreement with empirical prediction models whereas, for magnitude Mw 7.4, PBSs provide higher ground-motion estimates, as a consequence of directivity effects, amplified by the specific geometry of the portion of the NAF facing Istanbul.

Analysis of spectral ratios for estimating ground motion in deep basins

1996 ◽  
Vol 86 (3) ◽  
pp. 646-654 ◽  
Author(s):  
M. Dravinski ◽  
G. Ding ◽  
K.-L. Wen
Keyword(s):  
Resonant Frequency ◽  
Ground Motion ◽  
Three Dimensional ◽  
Sedimentary Basins ◽  
Spectral Ratio ◽  
Spectral Ratios ◽  
Resonant Frequencies ◽  
Ground Motion Amplification ◽  
Three Dimensional Models ◽  
Incident Waves

Abstract Use of Nakamura's spectral ratio (horizontal versus vertical components) is investigated theoretically for deep sedimentary basins by considering semi-circular and semi-spherical valleys. The ratio is evaluated from the steady-state surface response for different incident waves. Based on this ratio, both the resonant frequencies and ground motion amplification are determined. The results based on Nakamura's ratio are compared with those based on the sediment-to-bedrock spectral ratios (Kagami's ratio). The results show that for both two- and three-dimensional models, Nakamura's technique predicts well the fundamental resonant frequency, but it could not determine higher resonant frequencies of the basins. The error in Nakamura's estimate of the fundamental resonant frequency increases for stations near the valley center. For alluvial valleys considered in this article, Nakamura's ratio failed to predict accurately surface ground-motion amplification.

Seismic Zonation and Default Suite of Ground-Motion Records for Time-History Analysis in the North Island of New Zealand

2012 ◽  
Vol 28 (2) ◽  
pp. 667-688 ◽  
Author(s):  
Claudio A. Oyarzo-Vera ◽  
Graeme H. McVerry ◽  
Jason M. Ingham
Keyword(s):  
New Zealand ◽  
Ground Motion ◽  
Time History ◽  
Time History Analysis ◽  
Seismic Zonation ◽  
The North ◽  
History Analysis ◽  
Ground Motion Records ◽  
Site Classes ◽  
Selection Of

A seismic zonation to be used in the selection of ground-motion records for time-history analysis of buildings in the North Island of New Zealand is presented. Both deaggregations of the probabilistic seismic hazard model and the seismological characteristics of the expected ground motions at different locations were considered in order to define the zonation. A profile of the records expected to apply within each zone according to the identified hazard scenarios is presented and suites of records are proposed for each zone, based on region-wide criteria, to be used in time-history analysis in the absence of site specific studies. A solution for structures with fundamental periods of between 0.4 and 2.0 seconds is proposed, considering a 500-year return period and two common site classes (C and D, according to the New Zealand Loadings Standard).

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